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Lancia Integrale Evo 2 16v head prep

Posted: November 19th, 2006, 5:02 pm
by Guy Croft
A couple of shots of a 16v Integrale Evo 2 head I am preparing.

Brief is optimum flow for high lift cams, high (30 psi) boost. it's straightforward to get improvements in the 136 (std bare port flow) to 150 or so, but beyond that the porting has to be done with great care (and takes MUCH longer). Rush it and you're going to break thru into a coolant gallery, and the higher the flow the more any deviation from a sleek internal aerodynamic profile fights against you.

To put 150 plus in perspective: in development terms the Integrale/Coupe 16v head is relatively straightforward to work on. By comparison, with a 16v Vauxhall XE 2 liter head, on the (1mm smaller) production 33mm valves that kind of flow (with a good valve-in response) is not easy to achieve, and if you get it and fit the right cams it's good for well over 238bhp even normally aspirated.

I think the most you're going to get out of an Integrale with OE size valves fitted is about 164, and to do that you're going to need to lift the valve to 13mm, anyone who claims much more, well, I'd like to see it in the flesh. And does it need more flow? Well, you can always chase more, but on a turbocharged engine? Not really.

There is no direct relationship between airflow on this engine and power, all I know is that a loss of airflow on the flowbench is a bad thing and reducing losses - especially at the high port velocity of a turbocharged engine is a good thing. I also know that a turbo engine will produce a lot more power for given boost than one that has not been gasflowed, and good valve-seat work will greatly enhance the throttle response.

But this job is not just performance enhancement, it includes inlet valve overhaul, race springs to replace the OE ones (for higher rpm limit) new Nimonic 80A exhaust valves to cope with the high exhaust temperature, new race guides, head reface etc.

The std head flow peaks around std cam lift of 8.2mm actual and springs coil bind at 11.6mm actual valve lift, so allowing even only 1mm safety clearance between coils (2mm is better) that means, for what it's worth, you could only put actually 10.6mm lift cams in a head with OE springs and get away with it.

I checked the shimming on the C&B cam and it looks like I need 1mm top hats on the inlet, which will shim in the mid range OE 33mm shims, that's fine. It's not a bad idea to have them anyway as the bucket gets very close to the head at 12.7mm lift without them.